Travellers who find themselves astray in some forest must not wander now this way now that

My second maxim was to be as firm and resolute in my actions as I could, and to follow no less constantly the most doubtful opinions, once I had determined on them, than I would if they were very assured, imitating in this travellers, who, finding themselves astray in some forest, must not wander, turning now this way now that, and even less stop in one place, but must walk always as straight as they can in a given direction, and not change direction for weak reasons, even though it was perhaps only chance in the first place which made them choose it; for, by this means, if they do not go exactly where they wish to go they will arrive at least somewhere in the end where they will very likely be better off than in the middle of a forest.

René Descartes, Discourse on Method and The Meditations (Penguin Classics, 1968) pp. 46-47

Beliefs are based much more on custom and example than on any certain knowledge

Having learnt from the time I was at school that there is nothiing one can imagine so strange or so unbelievable that has not been said by one or other of the philosophers; and since then, while travelling, having recognized that all those who hold opinions quite opposed to ours are not on that account barbarians or savages, but that many exercise as much reason as we do, or more; and having considered how a given man, with his given mind, being brought up from childhood among the French or Germans, becomes different from what he would be if he had always lived among the Chinese or among cannibals; and how, down to our very fashions in dress, what pleased us ten years ago and will perhaps please us again before another ten years are out, now seems to us extravagant and laughable, I was convinced that our beliefs are based much more on custom and example than on any certain knowledge, and, nevertheless that the assent of many voices is not a valid proof for truths which are rather difficult to discover, because they are much more likely to be found by one single man than by a whole people. Thus I could not choose anyone whose opinions it seemed to me I ought to prefer to those of others, and I found myself constrained, as it were, to undertake my own guidance.

René Descartes, Discourse on Method and The Meditations (Penguin Classics, 1968) p. 39